WASHINGTON, May 16 (Reuters) - U.S. Senator Elizabeth Warren, a Democrat seeking her party’s presidential nomination, on Thursday called for new rules governing Pentagon contractors, saying the industry has become too close to Defense Department officials.

Warren wants to limit the ability of former Pentagon officials to work for contractors or foreign governments and to make public the documents of private companies working with the Defense Department, she outlined on Thursday in a post on Medium.

Warren is one of more than 20 Democrats vying for her party’s nomination to challenge Republican President Donald Trump in the November 2020 election.

Warren has distinguished herself in the field as the candidate with the most prolific series of policy proposals on a myriad of topics. Many of Warren’s proposals have focused on limiting the influence of corporations in Washington.

Attempts to make any reductions in military spending - including to contractors - have been met with staunch opposition from Republicans, who have painted Democrats as weak on security.

The five largest Pentagon contractors — all of which would be affected by Warren’s proposal — are Lockheed Martin Corp , Boeing Co, General Dynamics Corp, Raytheon Co and Northrop Grumman Corp.

Warren, along with Democratic Representative Jackie Speier, filed legislation on Thursday that would achieve her desired overhaul of the rules. In the Democratic-controlled U.S. House of Representatives, the bill is more likely to gain approval, but stands a near-impossible chance of passage in the Republican-controlled Senate.

Warren argues the changes are necessary because the industry is too close to government officials and pushing for more spending, not to keep the nation safe, but to pad corporate profits.

“We have to call this what it is: corruption, plain and simple,” Warren wrote on Medium.

Defense contracting is a billion-dollar industry, with five companies largely dominating contracts that range from building jets to preparing food. A sprawling operation with a presence around the globe, the U.S. military relies on contractors to provide many critical and highly sensitive services.

First, Warren said she would limit the ability of high-ranking Pentagon officials to work for contractors that they supervise for four years after leaving the military. Any current contractor employee who returns to government work would be unable to supervise any contracts with their former employer.

Next, Warren said she would limit the ability of retired military officials from working for foreign-owned companies. She would also prohibit “former military and civilian intelligence officers” from working for a foreign government or any private company controlled by a foreign government.

Finally, Warren said she would make federal public records laws — the Freedom of Information Act — apply to military contractors. (Reporting by Ginger Gibson Additional reporting by Mike Stone Editing by Leslie Adler and Jonathan Oatis)